To the non-gamers of CC. Majority of Free to Play games are MMOGs (Massively Multiplayer Online Games). Some of them are more arena style games where you go in for 15+ minutes finish a round and get rewards. Some of them are RPGs (Role-Playing Game) and are a bit more time consuming and reward in the long run. So I've decided to make a list of some games I've tried and enjoyed.
RPG
Aion - A Korean created MMO that takes a long time to get anywhere. The pay off of it is completely free they don't make you pay for expansions.
Star Trek Online - A free and fun game set in the Star Trek universe 30 years after the events of Star Trek Nemesis. You can play as a Science officer, Tactical, and Engineer. You can customize your own race and ship. You can play as the Federation or Klingons. Through microtransactions you can buy ships or costumes for your characters. You can even work for them in a free method using in game currency.
Champions Online - A superhero MMO that lets you create a hero of your own imagination. You can create anything, a pirate to a ninja, a pimp to a fine ass honey.
All Points Bulletin: Reloaded - Remember playing Cops and Robbers as a kid? Always imagined yourself as a gun toting tattooed up criminal? Well now you can. One of the trade offs of subscribing is creativity.
You can even make a Che Guevara shirt!These really hit the Marx.Arena Style games
Team Fortress 2 - A multi class game with fast paced gameplay. Its a lot of fun and worth checking out.
World of Tanks - A WWII tank combat game. You can buy tanks with earned in game currency or spend money and buy them without the effort.
Mech Warrior Online - A mech based game that is a lot of fun. It is currently in Open Beta so not all the mechs are out yet. Just like World of Tanks you can earn your mechs with in game currency or spend money to get them.
Not so Free games
Guild Wars 2 - $60, but no subscription. You can play numerous classes with a handful of races. Its a lot of fun and really rewarding in a short amount of time. Type of RPG that feels like you can get a lot done even in just an hour. All items in its cash shop can be earned with in-game currency that can be traded into Gems which are used to buy cash shop items.
Eve Online - An optional subscription game that makes you work for its benefits. A game that requires a lot of thinking and has a lot of real world application to it such as politics, economics, and all out war. You don't have to pay for a subscription, but you do have to work by mining resources for long amounts of time. Not-so-fun fact about Eve: One of the Benghazi victims played and was well known in the game.